The invention concerns a detergent additive based on swellable layer silicates.
Detergent auxiliaries to enhance whiteness are known from DD-220326, 220326, 220327 and 220328. These contain optical brighteners and nonswellable layer silicates, for example, the natural mineral magadiite. The use of aluminosilicates of limited swellability in detergents that also contain optical brighteners is also known from DE-A-35 26 405.
A trend toward higher bulk densities has been witnessed since the mid 80""s in the development of detergents. The motive behind this is the possibility of reducing the use of excess volume-increasing fillers and saving packaging material. Another advantage is seen in the fact that smaller volume is essential in transport and marketing. The consumer has the advantage that detergent packages take up less room in the shopping cart.
An important step in the development of highly concentrated detergents with high bulk density is the omission of fillers or so-called extenders, like sodium sulfate.
DE-C-3 424 987 describes the production of detergent concentrates with high bulk density containing no sodium sulfate as an extender. In this case, a base powder is produced by spray drying, which contains the ordinary detergent ingredients, like surfactants, carboxymethylcellulose (CMC), sodium polyphosphate, zeolite A, water glass, optical brighteners, etc. The obtained base powder with low bulk density, which is free of sodium sulfate, is sprayed with an additional nonionic surfactant to increase the bulk density and mixed dry with a separately produced granulate with high bulk density. The optical brightener in this product is unprotected of contact, especially oxidation, by other detergent components.
Another serious shortcoming of highly concentrated detergents with high bulk density is the fact that the detergent components come in contact with each other in high individual concentrations without dilution with an extender. This was not the case in detergents with low bulk density that contained as much as 25% sodium sulfate. The active components of the detergent in detergent concentrates are tightly packed in high concentration. In an unfavorable case, the detergent components can react with each other during hydrolysis or oxidation, which can lead to an adverse effect on the function of the ingredients and the detergent.
Incorporation of optical brighteners in detergent concentrates with high bulk density poses a problem. In the production of detergents with low bulk density, the optical brightener was processed either in the sprayed product, or subsequently mixed as a powder into the tower product (sprayed product). If the optical brightener is not separated by a coating that forms during production, or by the presence of diluting, spatially separating and water-adsorbing extenders from the bleaching agents also contained in the detergent, like sodium perborate, but especially sodium percarbonate, the optical brighteners can be oxidized. The bleaching potential of the oxidized material is then no longer available for a later bleaching in the wash liquid. In addition, the oxidation product of the optical brightener can be colored yellow, so that the detergent, on the one hand, exhibits a yellow tint and, on the other hand, the yellow oxidation product of the brightener winds up essentially on the washed textiles, which adversely affects that aesthetic appearance, especially in white washing.
The formation of active oxygen in the detergent powder, which precedes oxidation of the optical brightener, is attributed to a reaction of the bleaching agent contained in the detergent powder, especially when percarbonate is the bleaching agent. In the presence of tetraacetylethylenediamine (TAED), peracetic acid is formed, from which active oxygen is liberated. This problem is described in M. Husslein et al., 36th International Conference 1994, WFK-Research Institute for Cleaning Technology e.V., page 82-85.
The problem was not serious in detergents with low bulk density that contained sodium sulfate because the water triggering the reaction could be bonded to sodium sulfate by formation of water of crystallization. However, the problem is very significant in detergents with high bulk density. A need therefore existed to protect optical brighteners, especially those of the stilbene type, from reaction with the active oxygen formed in the detergent powder.
Another problem accompanying the formulation of detergent concentrates is that the agglomerates with high bulk density do not dissolve quickly enough in the wash liquid and turn up in the washing liquid bottoms. Since sufficient mechanical stress on the agglomerates does not occur at that location, they only partially dissolve, so that the active components are partially deprived of detergent action.
Detergent agglomerates of high bulk density generally have poor dispersibility. This can be improved by adding dispersants and disintegrating agents, which swell on contact with water and break open or loosen the agglomerates, which leads to improved solubility and availability of the active components. It is described in an article of H. Fxc3xchrer, Seifen-xc3x96le-Fette-Wachse, 18(1963), pages 561-562, that natural smectites that swell in water can be used as disintegrating agents in compacted detergent tablets.
The presence of a disintegrating agent that disintegrates the detergent agglomerates is also necessary to avoid so-called xe2x80x9cbrightener spottingxe2x80x9d. Brightener spotting develops from longer contact of undissolved, brightener-containing agglomerates with the washing. By direct contact of locally superconcentrated optical brightener, this is transferred in locally restricted fashion to the fabric at the contact site in undesired high concentrations. This is particularly visible in the presence of UV light in the form of light spots and adversely affects aesthetic appearance.
Detergent agglomerates must therefore contain disintegrating agents in order to be broken apart on contact with the washing liquid, though which the optical brightener is dissolved homogeneously in the washing liquid and direct contact of the detergent agglomerate with the washing is avoided.
If several detergents of different formulas are produced in a production installation for detergents, problems develop when brightener-containing and brightener-free detergents are produced in the same installation. Brightener-free formulated detergents are contaminated with residues of the optical brightener in installations in which a brightener-containing detergent had been produced beforehand. Even with thorough preliminary cleaning of the installation, this contamination cannot be fully ruled out.
A demand therefore exists for a detergent additive, in which the brightener component can be incorporated appropriately in the detergent while avoiding contact with the important parts of a detergent production unit without adversely affecting the function of the optical brightener.
The underlying task of the invention is to prepare a detergent additive in agglomerate form (granulate form), which contains at least one swellable layer silicate and an optical brightener that breaks down readily in water at good mechanical stability, and in which the optical brightener is homogeneously distributed and protected against oxidation by the oxidation agents contained in the detergent.
The object of the invention is a detergent additive in agglomerate form, characterized by the fact that it contains at least one swellable layer silicate and at least one optical brightener in intimate contact with each other.